样本量n对总体总单位数N的比称为抽样比(sampling fraction)： 目标总体与抽样总体 目标总体（target population）：是真正作为研究对象的全体。
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抽样比率 sampling ratio ; sampling fraction
统一抽样比 [统计] overall uniform sampling fraction
总抽样比 [统计] overall sampling fraction
抽样比例 sampling fraction ; sampling proportion
最优抽样比 optimum sampling fraction
抽样比重 sampling portion
层内抽样比 sampling fraction in the stratum
一级抽样比 [统计] primary sampling fraction
色相抽样比率 YCbCrSubSampling
调查表明，布莱顿居民的平均寿命为78岁，比15个抽样城市的居民平均寿命长一年。
It said Brighton residents lived to an average of 78 years, a year more than the average of the 15 sampled cities.
而页级的抽样则可以显著减少 I/O，因为它只读取一定百分比的数据页。
Page level sampling reduces I/O significantly since it reads only a percentage of the data pages.
行级的抽样读取所有数据页，但是只考虑每页上一定百分比的行，因此只包含相应xda页面中的一部分。
Row level sampling reads all data pages but considers only a percentage of the rows on each page, and therefore only a subset of the corresponding XDA pages.
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